How Can Severe Pain In The Knees Due To An Injury Be Treated?

I fell some black ice going into my car and I fell on my left knee. had a difficult time getting up. Now ever time I bend my knee especially when I sit down or try to get up. Especially from the toilet, my knee is in severe pain. This happened at work this evening in their parking lot and no lighting in that area so it was black ice that I slipped on because it was dark out and I could not see. I have complained just about 2 weeks ago that there was not enough lighting in the parking lot. I am not one to complain and keep going even when my body is in pain . I am in human resources and have worked for this company for 30 plus years. I feel like this is more than a bruise on my knee because the pain is inside the knee not on the surface. Do you think I should have an MRI? Or do you think I should wait and see if it improves?